Aerodynamic vehicle



Jan. 28, 1964 J. N. NIELSEN AERODYNAMIC VEHICLE Filed July 15. 1960INVENTOR JACK N. NIELSEN ATTORNEYS United States Patent O 3,119,576AERODYNAMZC VEHEQLE Jack N. Nielsen, Pale Aito, Caliti, assignor to ItekCorporation, a corporation of Delaware Filed July 15, Edit), Ser. No.43,163 5 Claims. (Cl. 244--1) This invention relates to improvements inaerodynamic vehicles and more particularly to a method and mechanism forproducing trim lift and side force on a re-entry vehicle utilizingseparated flow induced by a blunt flare.

Due to the present scientific and other interest in recoveringaerodynamic bodies from space flight, considerable emphasis has beenplaced on constructions of re-entry vehicles. The practical achievementof flight speeds of space vehicles through air causes aerodynamic bodiesto burn through friction created by movement through the air at highspeeds, i.e., aerodynamic heating as occurs on meteors, unless specialmeans are taken to prevent this burning. One eifective way of reducingor eliminating burning is to increase the aerodynamic drag of thevehicle in proportion to its weight. This increase in aerodynamic dragcan clearly be achieved through the use of flares or body flaps on thebody. This known construction reduces the cooling requirements and theamount of burning and also acts to stabilize the vehicle in flightsomewhat in the same fashion as a badminton shuttlecock is stabilized byits flared feathers.

The beneficial effect of a body flare in preventing burning due toaerodynamic heating increases as the flare angle increases as long asthe aerodynamic flow follows the body contours smoothly and does notseparate therefrom. However, with a blunt nosed capsule and with asufliciently large flare angle, the flow will separate. It is known,both theoretically and experimentally. that flow separation reduces thecooling load in a separated flow region to about one-half that forunseparated flow. Such reduced cooling load is a result of the reducedvelocities of the airflow in the proximity of the body. Separation alsohas the effect of reducing the static pressure acting on the flare inthe region of separation below that which would act in the same regionwith attached flow and below that which acts on the reattached area ofthe flare. By suitable control over the extent of the reattached flowarea on the flare by the means outlined in this application, theseparation can be made to yield further benefits, in addition to thoseof reduced cooling load, of enhanced sttability and of the production ofcontrol forces for the purposes of maneuvering. Accordingly, it is theob ect of this invention to provide a maneuverable aerodynamic re-entryvehicle including blunt capsule and flare, which vehicle has increasedstability and requires a decreased heat load accomplished by controlleduse of flow separation, thereby achieving a weight saving since theweight of the cooling system or cooling material is reduced and the sizeof the flare may be reduced.

It is also an object of this invention to provide a means for producingtrim lift and side force on an aerodynamic body for maneuverability byutilizing separated flow induced by a blunt flare by controlling thepitch and yaw angles of a flare axis relative to a capsule axis.

Other objects and advantages of this invention will be pointed out inthe following description and claims and illustrated in the accompanyingdrawings, which disclose, by way of example, the principles of thisinvention and the best mode which has been contemplated of applyingthese principles.

In the drawings:

FIG. 1 is a diagrammatic illustration of a blunt capsule and rigidlyattached flare type of aerodynamic body illustrating separation of flow;

3,1195% Patented Jan. 28, 1964 ICC FIG. 2 is a somewhat schematicillustration of the maneuverable aerodynamic vehicle of this inventionwith a portion broken away to show a capsule attached to a flare bymeans of a joint allowing limited universal movement therebetween;

FIG. 3 is an end view illustrating the areas of attached flow and thelocation of the center of gravity relative to the center of pressure ofthe capsule and flare; and

FIG. 4 is a view similar in nature to FIG. 3 illustrating trimmed liftand sideforce as well as positive dihedral effect.

In general, this invention contemplates controlling and stabilizing anaerodynamic body such as a re-entry vehicle. The body is constructedwith a blunt nosed capsule and an attached rear flare. The flare is notrigidly attached to the capsule but is attached thereto by means of asuitable universal movement permitting joint such that the capsule maypitch and yaw relative to the flare. By means of this construction andusing the principles of separated flow, as well as correctly locatingthe center of gravity and the like, the pitching and yawing momentscaused by the lift and sideforce produced by flow separation andreattachment on the flare and caused by the lift and sideforce on thecapsule due to its movement relative to the flare will compensate andpermit trimmed stable flight of the vehicle, which can be maneuvered bymoving the longitudinal axis of the flare relative to the longitudinalaxis of the capsule. The resultant construction is an aerodynamicvehicle adapted for atmosphere re-entry purposes which requires minimumcooling due to separated flow, and utilizes the reattachment ofseparated flow for maneuverability, while having inherent aerodynamicstability.

Referring now to FIG. 1 for an understanding of the background of theinvention, FIG. 1 shows an aerodynamic body 16 having a blunt nose 12 ona capsule or substantially cylindrical body portion 14. Rigidly joinedto the body portion is a rear flare 16. This construction increases theaerodynamic drag with respect to the weight of the vehicle and helpsprevent aerodynamic burning. A separation of flow is illustrated in FIG.1 for a zero angle of attack. It can be seen that the flow separates atpoints S and S and reattaches itself to the flare at points R and R atthe shoulder of the flare. The area of the triangie between S R or S Rand the surface of the vehicle It is an area of separation of flow inwhich the static pressure acting on the body is greatly reduced and thecooling requirements are greatly reduced since there is no greatfriction created by the air rapidly moving over the body at this area.It is known that a favorable consequence of flow separation of this typeis the fact that the total heat transfer in the separated regions isabout half of what it would be for attached flow for both laminar andturbulent boundary layers. When the body illustrated in FIG. 1 isdisplaced from an equilibrium position of zero angle of attack, theseparation of flow will be greater on one side that on the other side ofthe vehicle. On the side of least separation, there will be a greaterarea of reattached flow on the flare. The static pressure acting on thereattachment area will be greater than in the separated region. As aresult the flare will produce a force behind the center of gravity whichtends to pitch (or yaw) the vehicle so that motion of the flare is fromthe side of lesser separation to that of greater separation. It is clearthat the forces developed on the flare tend to oppose the displacementfor zero angle of attack which brought about the asymmetrical separationdistribution. In this sense the flare produces stabilizing moments.However, in the displacement from zero angle of attack the force on thecapsule will develop a moment about the center of gravity which will nottend to oppose the displacement from zero angle. In this sense thecapsule produces destabilizing moments. To achieve stability for a givencapsule, it is only necessary to make the flare sufliciently large andblunt. Thus, to achieve favorable stability effects with flare-inducedseparation, it is necessary to control the center of gravity Withrespect to the two moments and the other geometrical variable such asthe length of the flare, the magnitude of the flare angle, and thelength of the body between the nose and the flare so that the forcescreated will balance.

Referring now to FIG. 2, a capsule portion 2 9 which houses a man orother payload is followed by a flare portion 22 which may be radiationcooled. The capsule 20 and flare 22 are joined together by a universalmovement permitting joint 24. The illustrated type of universal movementjoint 24 includes a plurality of actuating rods 26, 28, 29 activated bysuitable servo motors (not shown) within housing 30, which in turn isrigidly supported from capsule 20 by support 32. The outer ends of theactuating rods are attached to the flare 22 to cause movement thereof.The means of attachment may include slotted brackets 34, 36, etc.,mounted on the inside of flare 22. Of course, alternate constructions ofcontrolled universal movement permitting joints could be utilized withinthe spirit of this invention. With a universal joint the capsule andflare may move relative to one another to pitch the capsule relative tothe flare to obtain lift control and to yaw the capsule relative to theflare to obtain sideforce control.

Lift control is accomplished by utilizing the larger area of reattachedflow at the bottom of the capsule as viewed in FIG. 2 behind the point Rto create an upward force on the capsule at this point, that is, acounterclockwise movement about the center of gravity point C.G. Thecapsule is pitched upwardly so that the cone of separation of air flowcreates the reattached flow portion more on the bottom than on the topand, of course, the surface pressures are greater at the reattached flowarea than at the separated flow region. For aerodynamic reasons the axisof the cone of separation is aligned in the free stream direction andthe point of reattachment R is at the shoulder of the flare. Thedifferential pressures on the flare tend to turn the nose of the entirevehicle downwardly, i.e., produce a counterclockwise moment about thecenter of gravity. However, the capsule is pitched upwardly and thiswill cause lift to create an upload tending to turn the capsuleclockwise about its center of gravity. When the pitching moment due tolift on the capsule balances that due to the lift on the flare, atrimmed condition is reached. Trim is an essential feature of practicalcontrol and by suitably controlling the angle of the axis of the flarewith respect to the capsule, useful lift for maneuvering the vehicle maybe produced.

Not only can trimmed lift be obtained for practical control, but alsotrimmed sideforce can be produced. Reference may be made to FIGS. 3 and4 for an illustration of the method of producing combinations of trimmedlift and trimmed sideforce for maneuverability. FIG. 3 represents afront view of the vehicle with the capsule pitched in such a fashion asto cause lift but no side force. The shaded area R represents the areaof reattached flow on the flare. The impact pressures of the reattachedflow regions of the flare are, of course, greater than those in theseparated flow region. The positive lift on :the flare represented bythe disposition of the crosshatchcd area produces a nose-down momentabout a lateral axis through the center of gravity which just trims thenose-up moment due to the lift of the capsule.

To produce sideforce to the right the capsule must not only be pitchedupward relative to the flare but also laterally, as shown in FIG. 4. Thereattachment area is now disposed more to the left than to the right sothat a sideforce to the right will be produced by the impact pressureson the reattachment area as well-as by the static pressures on thecapsule. The vehicle will thus move toward the right in response to theside forces. There will be an alteration in the vehicle attitude,principally in its bank attitude, until the yawing moment about avertical axis through the center of gravity induced by the impactpressures on the flare will just balance the equal and opposite yawingmoment due to the forces on the capsule. In tl is new banked condition,the nose-up moment due to the capsule and the nose-down moment due tothe flare may no longer balance. Thus the vehicle may also change itspitch attitude as well as its bank attitude so that the net pitchingmoment for the vehicle will also be zero. It is thus through the motionof the capsule with respect to the flare both in pitch and yaw thattrimmed lift and sideforce for maneuvering are produced.

Consider now how a vehicle can be designed to possess positive dihedraleffect. While positive dihedral effect is not necessary for an automaticcontrol system, it is desirable in case of pilot control. The vehicle isdesigned so that the flare is a body of revolution, the center ofgravity of the vehicle is close to the flare axis (on the flare axisextended), and the capsule exhibits generally larger lateral extentsthan vertical extents in its cross sections. Consider now FIG. 3, withthe capsule deflected upward with respect to the flare in a trajectorydescending in a vertical plane toward the earth. Under thesecircumstances the capsule will be trimmed in pitch and it will have zeroyawing moment and zero rolling moment on it by symmetry. It can now beshown that if the capsule is displaced slightly about its longitudinalflare axis, it will right itself into the upright position and will notroll over on its back. Referring now to FIG. 4 with the whole vehicleslightly displaced from its equilibrium position, the forces which tendto produce rolling moments are those associated with the capsule solely.No rolling moments can be expected from the flare, a body of revolution,since all pressures acting on it act normal to its surface and throughits longitudinal axis.

It is clear that the lift or normal force will have a tendency to returnthe capsule to an upright position, whereas the sideforce being positiveto the right will have a tendency to roll the capsule over on its back.The magnitude of the lift as compared to the sideforce is controlled byproperly shaping the capsule cross section to provide requisite lift andthereby controlling this righting tendency. In particular theaerodynamic configuration is such that the lift force per unit angle ofattack is considerably larger than the sideforce per unit angle of sideslip causing a righting tendency which will return the capsule to theupright position. To accomplish this aerodynamically, the capsule issimply made greater in the horizontal dimension that in the verticaldimension, generally speaking. Of course, the flare 22 does not have tobe circular in section as there are a number of other cross sectionalshapes for producing the same result.

Thus applicant has disclosed a method and means of stabilizing anaerodynamic body of the type having a blunt capsule and a flared portionto control the trim as well as the side force, while stabilizing thebody about a longitudinal axis.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to the preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention. It is the intention,therefore, to be limited only as indicated by the scope of the followingclaims.

What is claimed is:

1. A maneuverable vehicle for travel in a fluid stream, said vehiclehaving a center of gravity, comprising:

a capsule;

nose means coupled to said capsule upstream of said center of gravityfor coacting with said fluid stream as said vehicle travels therein;

control means coupled to said capsule downstream of said nose means,said control means having a surface extendable externally from saidcapsule for cooperating with said nose means to create an area ofseparated flow adjacent to said capsule, said flow defining asubstantial conical surface of separation having a virtual apex in thevicinity of said nose means and defining a closed curve of attachment assaid conical surface of separation intersects said control surface, saidclosed curve being so disposed along said control surface tosubstantially balance about said center of gravity all aerodynamicmoments on said vehicle for providing substantially zero net momentabout said center of gravity when said control means surface is in aneutral position; and

coupling means for displacing said control means surface from itsneutral position to at least a second position to alter said area ofseparated flow whereby at least a portion of said curve is displaced toa second location on said surface for providing moments about saidcenter of gravity to produce attitude control and maneuverability whensaid vehicle travels in said fluid medium. 2. The combination of claim 1wherein said control surface is substantially conical.

References Cited in the file of this patent UNITED STATES PATENTS1,165,731 Webber Dec. 28, 1915 2,470,348 Haight May 17, 1949 2,584,826Wyckofi" Feb. 5, 1952 2,612,329 Crandall et al Sept. 30, 1952 2,719,683Jones Oct. 4, 1955 2,941,764 Lee et al June 21, 1960 3,047,259 Tatnallet al. July 31, 1962

1. A MANEUVERABLE VEHICLE FOR TRAVEL IN A FLUID STREAM, SAID VEHICLEHAVING A CENTER OF GRAVITY, COMPRISING: A CAPSULE; NOSE MEANS COUPLED TOSAID CAPSULE UPSTREAM OF SAID CENTER OF GRAVITY FOR COACTING WITH SAIDFLUID STREAM AS SAID VEHICLE TRAVELS THEREIN; CONTROL MEANS COUPLED TOSAID CAPSULE DOWNSTREAM OF SAID NOSE MEANS, SAID CONTROL MEANS HAVING ASURFACE EXTENDABLE EXTERNALLY FROM SAID CAPSULE FOR COOPERATING WITHSAID NOSE MEANS TO CREATE AN AREA OF SEPARATED FLOW ADJACENT TO SAIDCAPSULE, SAID FLOW DEFINING A SUBSTANTIAL CONICAL SURFACE OF SEPARATIONHAVING A VIRTUAL APEX IN THE VICINITY OF SAID NOSE MEANS AND DEFINING ACLOSED CURVE OF ATTACHMENT AS SAID CONICAL SURFACE OF SEPARATIONINTERSECTS SAID CONTROL SURFACE, SAID CLOSED CURVE BEING SO DISPOSEDALONG SAID CONTROL SURFACE TO SUBSTANTIALLY BALANCE ABOUT SAID CENTER OFGRAVITY ALL AERODYNAMIC MOMENTS ON SAID VEHICLE FOR PROVIDINGSUBSTANTIALLY ZERO NET MOMENT ABOUT SAID CENTER OF GRAVITY WHEN SAIDCONTROL MEANS SURFACE IS IN A NEUTRAL POSITION; AND COUPLING MEANS FORDISPLACING SAID CONTROL MEANS SURFACE FROM ITS NEUTRAL POSITION TO ATLEAST A SECOND POSITION TO ALTER SAID AREA OF SEPARATED FLOW WHEREBY ATLEAST A PORTION OF SAID CURVE IS DISPLACED TO A SECOND LOCATION ON SAIDSURFACE FOR PROVIDING MOMENTS ABOUT SAID CENTER OF GRAVITY TO PRODUCEATTITUDE CONTROL AND MANEUVERABILITY WHEN SAID VEHICLE TRAVELS IN SAIDFLUID MEDIUM.